Keratoconus is a degenerative disorder of an eye, which is characterized by a non-inflammatory thinning and steepening of the central and/or para-central cornea. These structural changes cause the cornea to become of a more conical shape than its normal gradual curve and lead to non-reversible visual impairment of the patient's eye when untreated. Keratoconus caused structural changes of the cornea also aggravate or even preclude a LASIK (Laser Assisted in Situ Keratomileusis) surgery, since a LASIK treated cornea with a further progressed keratoconus may lead to a cornea ectasias later on.
A patient's visual impairment caused by keratoconus may be corrected by specially adapted eyeglasses or corneoscleral contact lenses. These corrections, however, do not work for a keratoconus in a late stage of its pathogenesis. In this case, only a so-called corneal crosslinking can be performed, which may stop or at least decelerate the pathogenesis. A complete visual rehabilitation, in turn, is not possible.
Therefore, it is desirable to detect keratoconus as early as possible.
Besides keratoconus, other corneal degeneration impacting the biomechanical stability of the human cornea exists. For example, pellucid marginal corneal degeneration (short: PMD; also known as keratotorus) is a degenerative corneal condition, which is typically characterized by a clear, bilateral thinning (ectasia) in the inferior and peripheral region of the cornea. In particular, the center of the cornea shows normal thickness with an intact central epithelium, but the inferior cornea exhibits a peripheral band of thinning. The portion of the cornea that is immediately adjacent to the limbus is spared, usually a strip of about a few millimeters. Further, Bowman's layer of the cornea may be absent, irregular or have ruptured areas.
In the following, the term keratoconus may represent any corneal degeneration impacting the biomechanical stability of the human cornea. Therefore, throughout this specification, the more specific term “keratoconus” may be replaced by the more general phrase “corneal degeneration impacting the biomechanical stability of the human cornea” or by any term representing corneal degeneration impacting the biomechanical stability of the human cornea, such as “pellucid marginal corneal degeneration”.
Existing diagnosis systems and diagnosis methods for detecting keratoconus or other corneal degeneration impacting the biomechanical stability of the human cornea are merely based on a measuring of the topography of the cornea and a detection of a conical deformation in this topography. Therefore, the keratoconus or other corneal degeneration impacting the biomechanical stability of the human cornea can only be detected in a relatively late stage of the pathogenesis, in which the visual impairment of the patient is already advanced.